[0001] This invention relates to a method and apparatus for handling semiconductor wafers
used in the production of integrated circuit structures. More particularly, this invention
relates to a method and apparatus for handling semiconductor wafers in a manner which
will permit transporting of the wafer from one processing station to another without
handling of the wafer, thus reducing formation of loose particulate, and which also
permits processing of both the top and bottom surfaces of the wafer equally while
mitigating the effects of shadowing.
[0002] During the processing of semiconductor wafers such as silicon wafers to form integrated
circuit structures in and on the wafer, it is necessary to perform a number of processing
steps which require transport of the wafer to various apparatuses or chambers within
an apparatus. Conventionally this involves the direct physical engagement of the wafer,
either manually or by robotic means, to move the wafer between such apparatuses or
process stations.
[0003] Each such step of physical handling of the wafer can result in the dislodgment of
particulates from the wafer surfaces during such handling or other damage to the wafer
which can lead to in failure of some of the chips or dies, thus lowering the yield
of chips per wafer.
[0004] Integrated circuit structures are usually formed on or in one surface of a semiconductor
wafer. As a result, wafer handling and transfer methodologies have been developed
for processes which involve only one surface of a wafer, conventionally the upper
surface.
[0005] However, there is a growing amount of interest in processing both surfaces of a semiconductor
wafer during the construction of integrated circuit structures, and in particular,
the necessity to remove oxide films from the backside of wafers without surface contact
either front or back. To remove these oxide films that have been deposited, the wafer
face (the front surface) is conventionally pushed upward to some grounding surface,
thereby endangering the already processed surface with a contacting and rubbing motion
creating particulate.
[0006] Since the wafer is conventionally supported during processing by resting the bottom
surface of the wafer on a support surface, processing of the bottom surface by conventional
means can require turning the wafer over to expose the bottom surface. This not only
involves extra process steps, but even further direct handling of the wafer as well,
which can further add to the risk of damage to the wafer, e.g., from particulates
which may become dislodged from the wafer surfaces during such handling.
[0007] Furthermore, while supporting the wafer from the sides during processing rather than
the bottom would allow access to the bottom surface of the wafer for processing, it
is well known that the placement of any device or material near the wafer during processing
can cause severe "shadowing" of the process on the wafer, i. e. the placement of a
device or material adjacent the wafer during processing results in incomplete etching,
deposition, etc. in those areas of the wafer surface immediately adjacent such device
or material.
[0008] US-A-4,473,455 describes a wafer holding assembly wherein a number of wafers are
loaded onto a plate. Pedestal elements engage the backside surfaces of the wafers.
The wafers are held in the plate by clips which are attached to springs mounted on
the plate and which engage the ends edges and the edge of the front surfaces of the
wafers.
[0009] US-A-4,306,731 and US-A-4,779,877 disclose a wafer support assembly comprising a
wafer plate assembly having an aperture larger than the diameter of the wafer. Spring
clips comprising spring bands or spring wires carried by the wafer plate assembly
have arcuate ends which engage the wafer surfaces adjacent the edges of the wafer.
[0010] It is a principal object of the invention to provide a process and apparatus which
would permit transport of a wafer from one process station to another or from one
apparatus to another without direct handling of the wafer as well as in a manner which
would permit equal processing of both sides of a semiconductor wafer without increasing
the risk of shadowing of the wafer on either side of the surface of the wafer during
processing.
[0011] This object is solved by the apparatus and the method of claims 1 and 9, respectively.
[0012] The method and apparatus of the invention permits transporting of the wafer from
one processing station to another without direct handling of the wafer to reduce dislodgment
of particulate from the wafer during such handling as well as other damage to the
wafer from such direct handling.
[0013] Specifically, a wafer retaining means is used which support the wafer during processing
in a manner which mitigates the effects of shadowing by objects adjacent the wafer
during processing.
[0014] Also, this wafer retaining means permits equal processing of both the top and bottom
surfaces of the wafer.
[0015] Further features and advantages of the invention will be apparent from the following
description and accompanying illustrations.
Figure 1 is a vertical cross-sectional view of a retaining ring holding a semiconductor
wafer.
Figure 2 is a top view showing a semiconductor wafer being transported by robotic
means to a retaining ring storage station having one or more wafer retaining rings
stacked therein.
Figure 3 is a top view showing a semiconductor wafer supported by robotic means positioned
over the storage station containing one or more wafer retaining rings.
Figure 4 is a die section view showing a semiconductor wafer supported by robotic
means positioned over the storage station containing one or more wafer retaining rings
as in Figure 3 and also showing the position of a rotatable orientation or flat finding
platform onto which the wafer will be unloaded by the robotic means to permit the
wafer to be rotated to orient the flat edge of the wafer with respect to the retaining
ring.
Figure 5 is a top view showing the semiconductor wafer loaded on the orientation platform
with the robotic means being withdrawn.
Figure 6 is a side section view of the structure shown in Figure 5.
Figure 7 is a side section view showing the orientation platform lowering the semiconductor
wafer into engagement with the top retaining ring contained in the retaining ring
storage station.
Figures 8-10 are fragmentary top views showing, sequentially, the engagement of the
semiconductor wafer by metallic spring clips carried by the retaining ring.
Figure 11 is a fragmentary side section view of end of the tip of the clip which engages
the wafer edge.
Figure 12 is a fragmentary cut-away top view of the end of the tip of the clip which
engages the wafer edge.
Figure 13 is a side section view showing the top retaining ring in the retaining ring
storage station having a semiconductor wafer loaded therein and the entire storage
station being indexed upwardly to the plane of the robotic means and the robotic
means being extended to engage the top retaining ring and remove it from the storage
station.
Figure 14 is a top view showing the robotic means laterally moving the retaining ring
containing the semiconductor wafer away from the retaining ring storage means in preparation
for moving the retaining ring and semiconductor wafer therein to a processing station.
Figure 15 is a top view of an alternate embodiment of the wafer-engaging clip showing
a ceramic end piece bonded to the metal clip.
Figure 16 is a top view of another alternate embodiment of the wafer-engaging clip
showing an additional spring arm integral with the clip to eliminate the need for
a separate spring to urge the clip into yieldable engagement with the end edge of
the wafer.
Figure 17 is a side view of the retaining ring showing grooves formed in the side
thereof which may be engaged by the robotic means to transport the retaining ring
and wafer loaded therein from one process station or apparatus to another without
direct contact with the wafer.
Figure 18 is a fragmentary side section view of the wafer/retaining ring assembly
of the invention being held in a processing station.
[0016] Referring now to Figure 1, a semiconductor wafer 10 is shown which has been inserted
into a retaining ring 20, constructed of a metal such as aluminum, including anodized
aluminum, or a ceramic material such as alumina, or any other material which will
not interfere with processing of wafer 10.
[0017] Wafer 10 may be held within retaining ring 20 by engagement with tips 60 on the ends
of yieldable clip mechanisms 30 while the wafer is moved between processing stations
as well as being retained therein during a number of process steps without any direct
handling of the wafer after initial insertion and prior to removal of the wafer after
such processing steps.
[0018] The height or thickness of tip 60 on clip mechanism 30 will be about 6t where t =
the thickness of wafer 10, which usually ranges from about 0.71 to 0.81 mm , i.e.,
the height or thickness of ceramic tip 60 is dimensioned to not exceed about 6 times
the thickness of wafer 10 to minimize interference with the processing of both sides
of wafer 10. The depth of the grooved end surface 62 in which wafer rests when engaged
by clip mechanism 30, as will be described in more detail below with respect to Figures
8-12, will be about 3t, i.e., about three times the thickness of wafer 10, again to
minimize any interference with the processing of both sides of wafer 10.
[0019] As will be more clearly seen in subsequent figures, clip mechanisms 30, and tips
60 thereon, space the outer edge of wafer 10 from the inner diameter of retaining
ring 20. Tip 60 extends from clip mechanism 30 a distance of at least about 12.2
mm or greater to prevent retaining ring 20 from interfering with the processing of
wafer 10, i.e., which permits the wafer to remain mounted within the retaining ring
during processing as well as during transport from one processing station to another,
thus greatly reducing direct handling of the wafer in between processing steps.
[0020] Thus, even when the end of clip mechanism 30 is flush with the inner edge of retaining
ring 20, retaining ring 20 is still separated from the outer edge of wafer 10 by a
distance of at least 12.2mm-3t, where 3t is the depth of groove 32 in tip 60.
[0021] Therefore, the presence of retaining ring 20 around wafer 10 during processing of
the wafer will not result in "shadowing" of the processing adjacent the periphery
of wafer 10 in view of the spacing there between. In this regard, it will be further
noted that the engagement of wafer 10 by clip mechanisms 30 and tips 60 is symmetrical
with respect to the top and bottom surfaces of wafer 10, thus permitting equal access
and processing of both top and bottom surfaces.
[0022] Furthermore, as can be seen in Figure 2 and subsequent top views, the lateral profiles
of those portions of clip mechanisms 30 protruding from retaining ring 20, including
tips 60, are very small, which also materially reduces interference with the various
processing steps.
[0023] Referring now to Figure 2 and subsequent drawings, the loading of wafer 10 into retaining
ring 20 will be explained. In Figure 2, a wafer 10 is shown being transported on a
robotic means 70 in preparation for being loaded into a retaining ring 20.
[0024] Robotic means 70 includes a primary arm 72 and a secondary arm mechanism 76 pivotally
connected to arm 72 by a shaft 74 into which secondary arm mechanism 76 has been pressed
to permit rotation of secondary arm mechanism 76 by rotation of shaft 74 by external
means such as a belt (not shown) around shaft 74. Secondary arm mechanism 76 is generally
forked shaped having a pair of tines or fingers 78 thereon on which wafer 10 is transported
and which respectively carry pins 82 on the ends thereof. Secondary arm mechanism
76 may further comprise fluid power means 80 for laterally moving fingers 78 apart
or together which, together with pins 82, may be used in the engagement of retaining
ring 20 by robotic means 70, as will be described below.
[0025] As seen more clearly in Figure 5, robot means 70 may be provided with friction pads
84, which may be formed from soft plastic materials, which are mounted on the upper
surfaces of fingers 78 and which may be used to engage the underside of wafer 10 to
prevent slippage without, however, damaging the surface of wafer 10.
[0026] Figure 2 also shows further construction details of one of the wafer engaging clip
mechanisms 30 on retaining ring 20 which will be further described below in connection
with Figures 8-10.
[0027] As shown in Figures 3 and 4, robot arm mechanism 70 moves wafer 10 into position
over a rotatable orientation mechanism 90 comprising a platform or turntable 92 which
may be raised and lowered, as well as rotated, by a shaft 94 beneath platform 92.
When wafer 10 has been positioned by robot mechanism 70 over platform 92, shaft 94
is raised to remove wafer 10 from tines or fingers 78, as shown in Figures 5 and 6.
[0028] Still referring to Figure 4, raisable and rotatable orientation mechanism 90 is mounted
within a storage mechanism 100 which is capable of holding a number of retaining
rings 20 in a stacked relationship. As shown in the side views of Figures 4, 6, and
7, and in the top views of Figures 2, 3, and 5, a series of retaining rings 20 may
be stacked in retainer ring storage mechanism 100 which may comprise a circular from
104 having a series of shoulders 106 thereon on which the respective retaining rings
20 may be stored. A support shaft 108 may be provided to raise and lower mechanism
100.
[0029] Orientation platform 92 is concentrically positioned within retaining ring storage
mechanism 100 so that lowering of platform 92 will lower wafer 10 thereon into a position
horizontally flush with the uppermost retaining ring in storage mechanism 100 to permit
wafer 10 to be engaged by tips 60 on clips 30 on the uppermost retaining ring 20 within
storage mechanism 100 as will be described below.
[0030] Referring now to Figures 5 and 6, after loading of wafer 10 onto orientation platform
mechanism 90 and withdrawal of robotic mechanism 70, wafer 10 is rotated on platform
92 to orient the flat side 12 of wafer 10, with respect to retaining ring 20, for
purposes of future processing as is well known to those skilled in the arm using suitable
detection means such as the optical detector mechanism shown at 98 in Figure 5, or
other suitable means such as an LED or CCD array with emitter.
[0031] Either before or after the rotational orientation of wafer 10 is completed, shaft
94 lowers platform 92 and wafer 10 thereon into a position for engagement of wafer
10 by clip mechanisms 30 on retaining ring 20 as shown in Figure 7.
[0032] As shown in top views of Figures 2, 3, and 5, a plurality of fluid power cylinders
110, which may be either pneumatic or hydraulic powered, are spaced around retaining
ring storage mechanism 100 for engagement with clip mechanisms 30 via shafts 112,
respectively coupled to each fluid power cylinder 110. Cylinders 110 are activated
to laterally retract clip mechanisms 30, as will be described below, when a wafer
10 is lowered by platform mechanism 90 to the plane defined by the uppermost retaining
ring 20 in retaining ring storage mechanism 100.
[0033] Referring now to the sequential steps shown in Figures 8-10 for engagement of wafer
10 by clip mechanisms 30, it will be seen that clip mechanisms are carried in cutaway
portions of retaining ring 20 with only a small portion of the clip mechanism protruding
from retaining ring for engagement with wafer 10. This serves to reduce any interference
by the materials comprising clip mechanism 30 with the subsequent processing of wafer
10.
[0034] As shown in Figure 8, fluid power cylinder 110 is shown in an inactivated position
with shaft 112 withdrawn from contact with clip mechanism 30.
[0035] Clip mechanism 30, in the embodiment shown in Figures 8-10, may comprise an aluminum
or stainless steel crank member 32 pivotally mounted at pivot pin 40 to retaining
ring 20. A spring 50, having a first portion 52 resting on the outer edge of retaining
ring 20, has a second portion 54 which is yieldably urged against a first arm 34 of
crank member 32 to maintain crank 32 normally in the position shown in Figure 8. A
second arm 36 on crank 32 is urged by spring 50 against a second pin 44 which acts
as a stop to limit the rotational travel of crank 32.
[0036] Fitted into an opening in the end of arm 34 is tip 60 which may be constructed of
a metal such as aluminum, which may or may not be anodized, or a ceramic material
such as alumina or to minimize any interference with the processing wafer 10 which
is contacted by tip 60. As best seen in Figures 11 and 12, ceramic tip 60 is provided,
at its end, with a concavely radiused or curved groove 62, i.e., a groove which, in
side section may be v-shaped, as seen in Figure 11, and which, when viewed from the
top, as seen in the cutaway top view of Figure 12, preferably closely matches the
radius of the wafer edge, i.e., the curvature of the wafer when viewed from the top.
This curvature of groove 62 will distribute the force exerted against the wafer by
clip mechanism 30 when tip 60 is brought into contact with the end edge of wafer 10.
[0037] Figure 15 illustrates an alternates embodiment of clip mechanism 30 in which a ceramic
tip 60′ is fitted to a cutaway portion of arm 34 and then suitably fastened to the
side of arm 34 by bonding or the like.
[0038] In Figure 16, the embodiment shown in Figure 15 has been further modified. Spring
50 has been replaced by a yieldably arm 35 which is integral with crank 34 rather
than a separate member.
[0039] Turning now to Figure 9, when wafer 10 has been lowered by platform mechanism 90
to a vertical position for loading wafer 10 into retaining ring 20 (Figure 7), fluid
power cylinders 110 are activated to urge shafts 112 thereon into engagement at 114
with crank 32. The point of contact 114 of shaft 112 with crank 32 comprises a third
arm 38 which is dimensioned in thickness to be thin enough to be slightly yieldable
when shaft 112 bears against it for a purpose which will be explained below.
[0040] The movement of shaft 112 against arm 38 of crank 32 causes a clockwise rotation
of crank 32 against the spring bias of spring 50 until arm 36 comes to a stop against
retaining ring 20 at 28. This clockwise rotation of crank 32 causes arm 34 on each
of the clip mechanisms mounted in retaining ring 20 to be withdrawn to a position
which permits wafer 10 to be lowered to a horizontal plane which vertically bisects
retaining ring 20 without interference from clip mechanisms 30.
[0041] Once wafer 10 reaches this position, fluid power cylinders 110 may be inactivated
resulting in a withdrawal of shafts 112 from engagement with arms 38 on respective
clip mechanisms 30. This permits spring 50 on each clip mechanism to urge crank 32
in a counterclockwise direction which moves arm 34 on crank 32 back toward the end
edge of wafer 10 until tip 60 on arm 34 contacts wafer 10 as shown in Figure 10. At
this point wafer 10 is yieldably secured in retaining ring 20 by clip mechanisms 30,
and more particularly by the spring bias of springs 50.
[0042] When fluid power cylinders 110 are inactivated, the spring bias of spring 50 could
cause arm 34 on crank 32 into a snapping engagement against wafer 10 which might result
in damage to the wafer. However, the yieldable engagement of shaft 112 with arm 38
muffles or dampens the counterclockwise movement of crank 32 since the compression
of arm 38 must first be removed before crank 32 will move.
[0043] Once clip mechanisms 30 on retaining ring 20 have been released to engage the end
edges of wafer 10, as shown in Figures 10 and 13, robotic means 70 may be moved into
position to engage retaining ring 20 by insertion of pins 82 (or 82′) on the ends
of fingers or tines 78 of secondary arm mechanism 76 into sockets 24 or grooves 24′
on retaining ring 20, as shown, respectively, in Figures 2, 5, 14, and 17. At the
same time support shaft 108 lowers retaining ring storage mechanism 100 to permit
removal of the retaining ring 20 engaged by robotic mechanism 70.
[0044] When the openings in retaining ring 20 comprise grooves 24′, as shown in Figures
5, 14, and 17, robotic means 70 may be moved toward retaining ring 20 with fingers
78 in an extended position until contact is made with retaining ring 20 after which
fingers 78 may be drawn toward one another by lateral movement means 80.
[0045] Alternatively, when the openings in retaining rings 20 comprise sockets 24, as shown
in Figure 2, fingers 78 are moved toward one another or apart, as the case may be,
until pins 82 on fingers 78 are aligned with sockets 24 in retaining ring 20 after
which robotic means is laterally moved to insert pins 82 into socket openings 24.
[0046] To retain pins 82 or 82′ in either sockets 24 or grooves 24′ during subsequent movement
of robotic means 70 to transport retaining ring 20 and wafer 10 mounted therein, lateral
movement means 80 may then be energized to exert lateral pressure on the respective
sidewalls of sockets 24 or grooves 24′ by pins 82 or 82′.
[0047] Robotic mechanism 70 may now transport the assembly comprising wafer 10 mounted in
retaining ring 20 to a first process station generally indicated at 120 in Figure
18 by the broken away portions of walls 122 and opening 124. Robotic mechanism 70
may then deposit the wafer/retaining ring assembly on a cathode 130 in first processing
station 120 and then robotic mechanism 70 is withdrawn from the processing station.
[0048] Either the top surface, bottom surface, or both surfaces of wafer 10 may now be suitably
processed to construct integrated circuit structures therein. For example, as shown
in Figure 18, the lift pins 132 in cathode 130 may be extended to clamp retaining
ring 20 against anode 140 which is maintained at ground potential, thus effectively
grounding wafer 10 while cathode 130 functions as the driven plane for processing
of the backside of wafer 10. For this application, of course, it will be necessary
that both ring 20 and tip 60 on clip mechanism 30 be constructed of metal or other
electrically conductive materials to achieve the desired grounding of wafer 10.
[0049] When it is desired to remove the wafer/retaining ring assembly from the first processing
station to move the assembly to a second station for further processing, lift pins
132 are withdrawn to lower wafer 10 back to the surface of cathode 130 and robotic
mechanism 70 may then be used to reengage retaining ring 20 via sockets 24 therein
and the wafer/retaining ring assembly is again transported to another processing station.
[0050] After all desired processing steps have been carried out, the wafer may be removed
from the retaining ring by a reversal of the steps described above for insertion
of the wafer into the retaining ring.
[0051] Thus, in accordance with the invention semiconductor wafer 10 may be transported
to any number of processing stations where one or both sides of wafer 10 may be processed,
i.e., etched, or have a layer of material deposited thereon or removed therefrom,
etc. without any direct handling of the wafer and without interference from the retaining
means used to engage the wafer, both in transport from one processing station to another
as well as during actual processing in a particular processing station.
[0052] It should be further noted that the use of retaining ring 20 to engage wafer 10
need not be limited to operations such as depositions and dry etchings normally carried
out in a single station or multiple station vacuum apparatus. Rather it is envisioned
that wafer 10 may also be retained within retaining ring 20 during other process steps
as well such as, for example, application, patterning, and removal of photolithography
materials (photoresists), wet etching, etc. In the latter case, of course, care must
be taken in selection of the type of material from which retaining ring 20 will be
constructed to ensure that the retaining ring is not attacked by the etchant.
[0053] Basically, the features which a retaining ring constructed in accordance with the
invention should include are: provision on the retaining ring for engagement of the
ring by remote means to permit the retaining ring and wafer mounted therein to be
transported from one processing station to another without direct handling of the
wafer; a ring with an inner diameter sufficiently large to permit processing of both
sides of the wafer equally without interference from the ring; and provision of a
low profile releasable wafer engagement mechanism on the ring to permit the end edges
of the wafer to be grasped by the retaining ring, with little if any interference
with the processing of the wafer.
[0054] Thus, while the invention has been described with regard to specific embodiments
of construction of the retaining ring of the invention, it will be understood that
modifications of the retaining ring itself, including the means for grasping the wafer
as well as the means used for engaging the retaining ring for remote transport may
be made without departing from the spirit of the invention.
1. Apparatus for handling semiconductors wafers (10) including means supporting said
wafers (10) during production of integrated circuit structures, characterized by:
a) a retaining ring (20) having engagement means (24;24′) thereon to permit said retaining
ring (20) to be engaged to transfer said wafer and said retaining ring from one processing
station to another to perform one or more processing steps on one or more surfaces
of said wafer (10);
b) means (30) on said retaining ring (20) for engaging the end edges of said wafer
(10) leaving both the top and bottom surfaces of said wafer exposed for processing;
and
c) an inner diameter on said retaining means sufficiently larger than the outer diameter
of said wafer to permit equal processing of both sides of said wafer without interference
by said retaining ring.
2. The apparatus of claim 1 wherein said means (30) for engaging the end edges of
said wafer (10) include clip means (30) carried by said retaining ring (20) and activatable
to yieldably engage the end edges of said wafer (10) after insertion of said wafer
(10) into said retaining ring (20).
3. The apparatus of claim 1 or 2 wherein means (90,92,98)) are further provided for
radially orienting said wafer (10) preferably comprising a rotatable platform (92)
prior to engagement by said retaining ring (20).
4. The apparatus of claim 3 which further includes storage means (100) for removably
storing a plurality of said retaining rings (20) in a vertical stack, including means
(108) to lower said storage means (100) with respect to a wafer (10) once said wafer
(10) has been loaded into said retaining ring (20) in said stack and wherein said
rotatable platform (92) is concentrically mounted within said storage means (100)
and is provided with means (94) for lowering said wafer (10) into a position for engagement
with a retaining ring (20) stored in said vertical stack in said storage means (100).
5. The apparatus of claim 4, wherein said apparatus further comprises robotic means
(70) for engaging said engagement means (24;24′) on said retaining ring (20) to permit
said retaining ring (20) and said wafer therein to be moved without contacting said
wafer (10) from one processing station to another said robotic means (70) engaging
preferably a fixed point (24;24′) on said ring (20) to which a flat side portion of
said wafer (10) is radially oriented.
6. The apparatus of any preceding claim wherein said engaging means on said retaining
ring are clip means (30) carried by said retaining ring (20) and activatable to yieldably
engage the end edges of said wafer after insertion of said wafer (10) into said retaining
ring (20) an inner diameter on said retaining ring (20) being sufficiently larger
than the outer diameter of said wafer (10) to permit equal processing of both sides
of said wafer (10) without shadowing by said retaining ring.
7. The apparatus of claim 6 wherein said clip means (30) carried by said retaining
ring (20) further comprise tip means (60) thereon constructed of a metal or a ceramic,
said tip means (60) having a groove (62) therein to yieldably engage the end edges
of said wafer (10), said groove (62) on said tip means preferably having a curvature
therein substantially the same as the radius of said wafer (10) to distribute the
force exerted by said clip means (30) against said wafer (10).
8. The apparatus of claim 6 or 7, wherein both said retaining ring and said clip means
(30) including said tip (60) thereon comprise electrically conductive materials to
permit grounding said wafer (10) by contacting said retaining ring (20) to ground
it.
9. A method of handling semiconductors wafers used for the production of integrated
circuit structures which permits moving said wafer from one processing station to
another without direct handling of said wafer and which also permits equal processing
of both the top and bottom surfaces of the wafer which comprises the steps:
a) inserting said wafer into a ringtype retaining means having an inner diameter sufficiently
larger than the outer diameter of said wafer to permit processing of both sides of
said wafer without shadowing by said retaining ring;
b) engaging the end edges of said wafer with yieldable means carried by said retaining
means for engaging the end edges of said wafer leaving both the top and bottom surfaces
of said wafer equally exposed for processing; and
c) contacting said retaining means with remote means to transfer said wafer and said
retaining ring from one processing station to another to perform a plurality of processing
steps on one or more surfaces of said wafer.
10. The method of claim 9 including the further steps of:
a) radially orienting said wafer prior to inserting said wafer into said retaining
means;
b) activating said yieldable means in said retaining ring to yieldably engage the
end edges of said wafer after insertion of said wafer into said retaining means; and
c) releasing said wafer from said retaining ring upon completion of said processing
steps; and
wherein said step of contacting said retaining ring to transfer said wafer and said
retaining ring from one processing station to another further comprises engaging one
or more fixed points on said retaining means to which a flat side portion of said
wafer is radially oriented.